1. Field of the Invention
The invention relates to method and apparatus for verifying positive inflation of inflatable tools such as packers. More particularly, the invention relates to installing sensors within the inflatable tool, connecting the sensors to a controller which when it receives information from the sensors communicates the information to the surface using a device or procedure capable of so communicating.
2. Prior Art
Past methods for verifying positive inflation of inflatables such as an external casing packer (ECP) have been to monitor the pressure gauge employed to measure the applied pressure to inflate the packer. The applied pressure is provided either through an internal tubing string using an inflation tool or by pressuring the casing string in which the ECP is installed. When the ECP opens and begins inflating, fluid in the pressurized column begins to rapidly disperse in an amount equal to the displacement of the inflating packer. Where the ECP is large or is being inflated in a hole that is significantly larger than the outside diameter of the ECP in the uninflated condition the displaced fluid is of a relatively large volume. A large volume of fluid moving out of the pressurized column creates a pressure drop. The pressure drop occurs suddenly and is recognized by the gauge measuring the applied pressure. As long as the displaced volume is large the pressure drop is easily measured and noted and the setting of the packer is confirmed with high confidence. The method has been used for many years successfully and reliably on all larger ECP applications. Unfortunately, however, where the ECP is being set in a hole not much larger than its own uninflated outside diameter, the amount of fluid displaced into the packer is too small to be recorded by the gauge monitoring the applied pressure. This is not to say that the displaced fluid does not actually produce a pressure drop because indeed it does, it simply is to say that the drop in pressure is small because the displacement of fluid is small and the gauge employed to monitor applied pressure at many locations does not have sufficient resolution to detect the drop. Inflation of ECP's set in this type of environment cannot be confidently verified.
One prior art method that has been attempted to confirm positive inflation of an ECP in a hole not much larger than its own uninflated outside diameter is to measure displaced fluid from surface tanks. In situations where there is a long fluid column however, and the amount of fluid for inflation is very small the percentage of fluid depletion in the tanks may not be within a measurable range with equipment common at drilling sites. Therefore, the art is in need of a system for confidently verifying inflation of an inflatable tool such as an ECP which is inflated with a relatively small amount of displaced fluid.
Another prior art method to provide information about ECPs is not direct, but as a confirmation system. More specifically, memory pressure gauges are placed in an inflation tool and measure pressure in the packer. The gauges remember the pressure and can be downloaded after removal of the packer. Drawbacks to the system are that there is no real time information and the gauges only measure pressure. They do not in fact measure whether or not inflation has taken place. Thus the information supplied is helpful but not conclusive and not timely.